Systemic mastocytosis diagnostic criteria (WHO/ICC)

Applies the major + minor criteria for systemic mastocytosis: SM if the major criterion + ≥1 minor, OR ≥3 minor criteria.

Evidence tier: Guideline-derived.

Formula / logic

Systemic mastocytosis is diagnosed when the MAJOR criterion plus ≥1 MINOR criterion are met, OR when ≥3 MINOR criteria are met. Major: multifocal dense MC aggregates (≥15 MCs). Minors: >25% atypical/spindled MCs; activating KIT mutation; aberrant CD25/CD2/CD30; baseline tryptase >20 ng/mL.

Interpretation

The tryptase minor criterion is not valid in the presence of an associated myeloid neoplasm and should be adjusted when hereditary alpha-tryptasemia raises baseline tryptase.

Evidence & citations

  1. Valent P, Akin C, Hartmann K, et al. Updated Diagnostic Criteria and Classification of Mast Cell Disorders: A Consensus Proposal. Hemasphere. 2021;5(11):e646. PMID 34901755

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